Insulator and method of manufacturing the same



Jan. 1939. J. J. TAYLOR 2,142,422

INSULATOR AND METHOD OF MANUFACTURING THE SAME Filed Nov. 10, 1936 INVENTOR BY L/O/7/7 Tag/or ATTORNEY Patented Jan. 3, 1939 INSULATOR AND METHOD OF MANUFAC TUBING THE SAME John J. Taylor, Wadsworth, Ohio, assignor to The Ohio Brass Company, Mansfield, Ohio, a-corporation of New Jersey Application November 10, 1936, Serial No. 110.073

'11 Claims.

This invention relates to electrical insulators and to a method of manufacturing the same, and

' has for one of its objects the provision of a hollow insulator within which electrical discharges will not occur.

A further object of the invention is to provide an improved means for filling the hollow insulator with an insulating gas and sealing the same to retain the gas within the insulator.

A further object of the invention is to provide an insulator which shall be of improved construction and operation and an improved method for manufacturing the same.

Other objects and advantages will appear from the following description.

The invention is exemplified by the combination and arrangement of parts shown in the accompanying drawing and by the steps of the process explained in the specification, and it is more particularly pointed out in the appended claims.

In the drawing:

Fig. 1 is a somewhat diagrammatic elevation with parts in section of an insulator and one form of apparatus for filling the same in accordance with the present invention.

Fig. 2 is a fragmentary top plan view of a portion of the apparatus shown in Fig. 1.

Fig. 3 is a fragmentary sectional view of an insulator seal made in accordance with the present invention.

In Fig. l of the drawing, the numeral l0 designates a post insulator made of porcelain or other suitable dielectric material, the insulator having an internal cavity I I to conserve the material and facilitate manufacture, as will be understood by those skilled in the art. It will be understood of course that the invention applies to various other forms of hollow insulators as well as that illustrated in the drawing.

It has been found that during operation of hollow insulators, where the interior of the insulator communicates with the atmosphere, moisture frequently condenses within the inner space, reducing the insulation provided by the dielectric member and giving rise to internal discharges. To avoid this difiiculty, it has heretofore been suggested to fill the interior of the insulator with an inert gas such as carbon dioxide, nitrogen or even dry air, but dimculty hasbeen experienced in providing an effective seal to close the insulator cavity. Where rubber or other gaskets are used, the enclosed gas in time diffuses through the gasket and the filler becomes ineffective. Difilculty has also beenmricnced in clearing the interior of the insulator from all moisture and other objectionable substances and effecting a complete filling with the desired gas. In the present invention these difiiculties'are overcome by sealing the cavity completely during the firing 5v process and after the moisture has all been driven out by the heat of firing. The invention also comprises a method of filling the sealed-oi! space within 'the insulator without permitting communication with the atmosphere.

In order to accomplish the ends of the invention, a sealing plug I 2 is provided which fits against a bevelled seat l3 at the open end of the insulator. Both the insulator and the plug I! are made of vitreous material, such as porcelain, 5: and are coated with a liquid glaze before the parts are placed in the kiln. The plug I2 is provided with a perforation H which extends nearly but not quite through the plug. This perforation may be drilled in the dried but unfired clay, but 20. extends only far enough to provide sufilcient porcelain at the point [5 to withstand atmospheric pressure after the parts are fired. The insulator with the plug 12 in place is placed in the kiln and during firing the glaze will harden and form a seal between the plug and its seat on the open end of the insulator. Prior to vitrification, the heat of the kiln will drive off all moisture from the body of the clay and also from the cavity II.

I Since the body of the clay is porous up to the so;

temperature of vitrification, the gas within the body II and the water vapor will be practically all driven from the interior of the insulator. When the temperature of vitrification is reached, however, the clay body will be sealed against any further passage of gas and at the same time the glazing material between the. plug l2 and its seat on the open end of the insulator will be vitrified, forming a gas-tight seal between the plug and the open end of the insulator.

Since vitrification takes place at a relatively high temperature, the chamber l I will be sealed off while filled with. a highly rarified atmosphere, and when the parts are cooled, the chamber II will be practically a vacuum. After cooling, a 46-. filler head it is placed over the perforation H, the filler head having a discharge mouth provided with a gasket I! of rubber or other similar material which can be pressed into tight contact with the portion of the plug l2 surrounding the per- 60 foration l4. Within the filler head I is a pin l8 which extends into the perforation l4 and contacts with the bottom of the perforation. The filler head It is connected by a flexible conduit I! to a source 20 of gas supply, such an carbon I! dioxide cylinder. Between the cylinder 2i? and the head l6 may be interposed a drying chamber 2| and a flow indicator 22. The head I6 is preferably mounted on a lever 23 or other operating mechanism, the lever being pivoted at 24 so that the head may be'readily moved into and out of operating position. The supply of gas from the tank 20 may be controlled by a valve 25. When the gasket ll is held firmly in place, a light blow on the top of the head It will cause the pin M to break the seal l5, as indicated at26 in Fig. 3.

If a perfect seal has been formed between the plug I and the insulator ll, sufficient gas will then flow from the chamber 20 into the interior of the insulator to fill the vacuum formed by the expansion of the gas during firing. This flow will be shown by the indicator 22. When the cavity H has been filled with the inert gas, the filler head 86 will be lifted and a cork 21 of proper size will be forced into the perforation M, as shown in Fig. 3. The portion of the perforation M not filled by the cork 21 may then be sealed by a suitable sealing wax or bituminous compound indicated at 28 in Fig. 3. Since the perforation It is quite small, practically no diffusion of gas will take place during the slight interval necessary to remove the head and insert the cork 21. Where a heavy gas is used, such as carbon dioxide, the insulator will be filled while in an inverted position, shown in Fig. 1. If it should be desirable t9 fill the insulator with a light gas, the position might be reversed, but in any event, very little interchange of gas can occur through the very small perforation M during the short interval of time necessary to remove the head and seal the opening.

If the cavity II is not perfectly sealed during the firing operation, air will enter the space I! during the cooling process so that the vacuum within the cavity will be destroyed before time to fill the insulator with inert gas. If such is the case, when the perforation is broken through, there will be no vacuum within the cavity and consequently no material flow of gas through the indicator 22. In this way the invention not only provides effective and convenient means for filling the insulator with an inert gas but also at the same time, means for detecting imperfectly sealed insulators.

I claim:

- 1. The method of manufacturing, from unfired ceramic material, an insulator having a cavity therein that may be sealed'by heating but from which gas may escape prior to sealing, said method comprising the steps of firing said insulator, expelling gas from said cavity by the heat of firing, sealing the'cavity during firing of the insulator and while the cavity is substantially free of moisture due to the high firing temperature, cooling the insulator after sealing and thus reducing the pressure within the sealed cavity, thereafter connecting the cavity with a supply of substantially dry gas to cause said gas to fill said cavity and finally sealing the gas within said cavity.

2. The method of manufacturing an insulator from unfired ceramic material, comprising the steps of forming the insulator with a cavity therein, said cavity having an opening thereto, placing a clbsure on said opening with a sealing medium interposed between said closure and the wall of said opening, firing said insulator to expel gas from said cavity and to cause said sealing medium to set, the heat of firing hermeticallysealing said cavity, cooling said insulator while said cavity is still hermetically sealed to reduce the pressure within said cavity and thereafter admitting a dry filling gas into said cavity to fill said cavity and restore the pressure therein and finally sealing said gas in said cavity.

' 3. The method of manufacturing an insulator from solid dielectric material, comprising the steps of forming an insulator with a cavity therein from which gas may escape but which may be hermetically sealed by heat, heating said insulator to expel a portion of the contents of said cavity and seal said cavity after the expulsion of said contents, thereafter perforating said insulator to provide communication to the interior of said cavity, admitting gas to said cavity through the perforation and finally closing said perforation to retain the gas within said cavity.

4. The method of manufacturing an insulator from unfired; ceramic material comprising the steps of forming said insulator with a closed pocket therein, heating said insulator prior to vitrification to expel gas from said pocket, sealing said pocket by vitrifying said insulator and thereafter introducing an insulating gas into said pocket and sealing said gas therein.

5. The method ofmanufacturing an insulator from unfired ceramic material comprising the steps of forming an insulator with a pocket therein from which gas may escape but which may be hermetically sealed by heat, heating said insulator to expel gas from said pocket and to seal said pocket by vitrification and thereafter filling said pocket with a non-conducting gas and sealing said gas therein.

6. The method of manufacturing an insulator comprising the steps of forming a porcelain body with a closed pocket therein and with a perforation extending only partially through the porcelain, firing said insulator to seal said pocket and thereafter breaking the porcelain to extend said perforation entirely through the porcelain into said pocket and permit access to said pocket.

7. The method of manufacturing an insulator from unfired ceramic material comprising the steps of forming an insulator body with a pocket therein from which gas may escape but which may be hermetically sealed by heat, firing said insulator and thus expelling a portion of the gaseous content of said pocket and sealing said pocket at a high temperature after the expulsion of gas therefrom, cooling said insulator to reduce the pressure within said pocket and testing said insulator by connecting said. pocket with a source of gas supply and by noting the flow of gas into said pocket clue to the reduced pressure therein.

8. The method of manufacturing an insulator comprising the steps of forming a body of unvitrified ceramic material having a pocket therein from which gas may escape but which may be hermetically sealed by heat, expelling gas from said pocket by heat, sealing said pocket by vitrifying the material of said insulator and thereafter connecting said pocket with a source of gas supply to fill said pocket and test the seal thereof.

9. The method of manufacturing an insulator, comprising the steps of forming a body'of unvitrified ceramic material having a pocket therein from which gas may escape but which may be hermetically sealed by heat, heating said body to expel gas from said pocket, vitrifying said material to seal said pocket, thereafter forming a perforation through the Wall of said pocket while excluding the atmosphere from said perforation, filling said pocket with an insulating gas through said perforation and thereafter sealing said perforation to retain said gas in said pocket.

10. In the manufacture of an insulator, the steps of heating a dielectric body having a pocket therein to expel gas from said pocket, hermetically sealing the pocket after the expulsion of gas therefrom and while said body is still heated. permitting the body to cool to create 'a partial vacuum in said pocket, connecting said pocket with a supply of non-conducting gas and permitting gas from said supply to enter the partial vacuum in said pocket, and thereafter sealing said pocket to retain said gas therein.

11. In the manufacture of an electric insulator,

15 the steps of heating a dielectric body having a pocket therein and a closure for said pocket, said closure having a perforation extending only partially therethrough, the heating of said body serving to expel gas from said pocket and to seal said pocket closed after the expulsion of gas therefrom, connecting a supply of non-conducting gas with the perforation in said closure and sealing said perforation at its point of connection, from the outer atmosphere, completing the perforation through said closure to permit gas from said supply to pass through said completed perforation into said pocket, and thereafter sealing said perforation to retain said gas in said pocket.

JOHN J. TAYLOR. 

